Archive: March, 2010
The reconnaissance jet has completed its work for the day, having dropped 16 data probes to measure some of the most-ferocious winds on Earth.
The storm that the Gulfstream IV was stalking at 45,000 feet has been affecting an extensive area from Alaska to central California, and the probes indicated that it was stronger than expected. One of the probes detected a jet-stream wind of 161 m.p.h. off the California
The remnants of that storm, which pounded that southwestern Canadian coast with hurricane-force winds, could affect Philadelphia by Sunday, says flight meteorologist Jessica Williams.
It was the second consecutive day that the Gulfstream, operated by the National Oceanic and Atmospheric Administration, dropped its data bombs into the upper-level system that is giving a kick to the storm calling all the mayhem at the surface
No flights are scheduled tomorrow, but it looks like the Gulfstream will be heading to a new trouble spot over the Northern Pacific on Sunday.
Earlier, I had described the probes as looking like paper-towel dowels. Actually, they are a tad bigger, about 18 inches long and 2 1/2 inches in diameter.
They weigh roughly two pounds each, and parachutes slow their descent to about 2 m.p.h. On the way down, they transmit data on wind speeds, temperature and pressure every half-second until the probe lands in the ocean, which was mightily agitated during the day with whitecaps visible all the way from 45,000 feet.
One of the dropsonde probes detected a wind of about 50 m.p.h. at the surface.
They work like upside-down weather balloons in an area where humans aren't available to release balloons.
The reconnaissance jet just passed over a jet-stream wind of 161 m.p.h., equivalent to a Category 5 hurricane, and then some.
The plane is making a loop through the upper-air low pressure system that is giving a kick to an impressive storm affecting an area from southern Alaska all the way to central California.
The plane is now on the western side of the storm center, and the winds, which were from the southwest, have backed around and now are from the west-northwest.
It storm is generating hurricane-force winds even at the surface near Vancouver. The winds at the surface below the aircraft are whipping up white caps on the Pacific, big enough to be visible from 45,000 feet.
Ultimately, it is not at all clear what the future of this system will mean for Philadelphia, but the flight meteorologist, Willow Grove's own Jessica Williams, says more heavy precipitation is possible early next week from some remnant of this feature.
As the plane makes a loop through the system, Charles Lynch, the crew engineer, is about to send out the 11th probe of the mission, with five more to go.
One big advantage these "data bombs" have over satellites is that the latter have a hard time seeing through cloud cover, which, of course, is standard fare in storms.
Weather balloons that profile the atmosphere are sent up every 12 hours. However, that data is lacking over lesser-developed countries and the oceans. Since weather moves west to east, the North Pacific is a crucial area for the United States.
Saturation bombing of the data-poor North Pacific would be prohibitively expensive, so the National Oceanic and Atmospheric Administration, which runs the Gulfstream program, has to pick its spots.
It looks for places where trouble is brewing, and where the computer models have wide disagreements on exactly what is unfolding there.
Today's trouble spot encompasses a tear-drop shaped area, about 1,600 miles long, from north of Honolulu to a latitude just north of Philadelphia's.
Typically, the jet flies missions every few days, but this is the second consecutive day that it has come out to look at this feature. Yesterday, it dropped probes to the north and west of today's reconnaissance area, and today it shifted the focus east with the storm.
The government jet prowling the atmosphere over the North Pacific now is riding above a solid cloud mass and probes directly into the upper-level weather system affecting Northern California.
The Gulfstream IV, operated by the National Oceanic and Atmospheric Administration, just flew over a jet-stream wind of 138 m.p.h., stronger than that of a Category 3 hurricane.
Those strong winds, measured about 1,600 miles northeast of Honolulu, are on the east side of the upper-level that is giving a kick to the system now affecting northern California.
That same feature may bring what flight meteorologist Jessica Williams describes as a "heavy precipitation event" to her hometown, Willow Grove, and the rest of the Philadelphia region by Sunday.
Her best guess right now would be rain, but coming up with a more-precise answer obviously is an important one, and Williams says that's one reason the Gulfstream IV is up here.
That wind reading is significant, because the U.S. computer model yesterday was forecasting a wind of about 120 m.p.h.
But the tiny computer board on the "dropsonde" device, about 18 inches long and 2 ½ inches in diameter, came back with the 138 m.p.h. real-time reading. That's a significant difference.
In the end, the details that can make all the difference in a forecast as a system moves downstream.
Over the North Pacific, where nature harbors some of its most-dangerous secrets, Charles Lynch is in the rear of a jet dropping bombs from 45,000 feet.
The "bombs" in this case are instrument packs, roughly the size of a paper-towel dowel, that are relaying wind, pressure and temperature data every half-second, from the high atmosphere all the way to the Earth's surface.
That data, in turn, is being relayed for use by computers all over the world for use in the models that forecast the weather.
The mission is to find out what mayhem the atmosphere has in mind today, tomorrow, next week.
The models depend on observations. They can't figure out what the atmosphere is going to do if they don't know what's happening now.
Those initial observations often are their Achilles heels.
And the North Pacific, one of the world's most-productive and dangerous storm factories, is one of the most-difficult places on Earth to obtain detailed weather observations.
That's why the National Oceanic and Atmospheric Administration is dispatching high-altitude flights to collect data in a fashion resembling an upside-down weather balloon. NOAA sends up planes every three or four days, sometimes every day, depending on what's out there.
The target area today is a Q-tip shape region ballooning from about 400 miles northeast of Honolulu out to about 1,600 miles, or roughly halfway to Alaska.
The jet is stalking a nasty looking, dragon-tail shaped cold front that is slamming into Northern California.
At a pre-flight briefing, meteorologist Jess Williams, a 27-year-old Willow Grove native, warns that this thing might end up bringing more heavy rain to the Philadelphia area early next week. She says this with all the calm of a flight attendant.
So far, the flight has encountered only minor turbulence, and Lynch, a NOAA engineer, has dropped four instrument bombs, with 12 more drops scheduled during the next several hours.
Later in the day, Williams says we will likely pass over jet-stream winds over 130 m.p.h. She said that's down from yesterday's 200 m.p.h.-plus.
The jet stream is crucial to the movement and development of storms.
The Category 5 hurricane-force winds can ignite storms -- think of the lifting effect of stiff winds passing over a smoking chimney.
In addtion, this torrents of air are the high speed highways that can take storms across the ocean, and across the country.
By the way, don't worry about the whales. The probes are light enough to be harmless on impact.
The temperature reached the big 6-0 yesterday, and the snowpack is all but history in the immediate Philadelphia area. Nonetheless, the National Weather Service advises that heavy rains could set off some flooding later in the week.
The water content of the snowpack in the headwater regions of the Schuylkill and Delaware River remains impressive, although some of that should get wrung out during the next two days.
This will be a slow-motion storm, with rain possible from late Thursday into Saturday. The fact that it will be a prolonged event, however, is not necessarily a bad thing.
Aesthetically, this is one of the year's most-underrated periods, with the still-bare swollen with buds and tinted ever so subtly.
But it also signals the onset of the torment season for tree-allergy sufferers. The trees are sending out their reproductive pollen, and about a million innocent people in the region may get caught in the cross-fire.
The Asthma Center's Dr. Donald J. Dvorin, the region's official pollen-counter, has begun posting the daily reports, and you can find his summary here.
It wasn't historically cold last month -- about three degrees below normal. In fact, for the meteorological winter, the period from Dec. 1 through Feb. 28, the overall Philadelphia temperature was quite close to normal.
Aside from the unbelievable snows, what distinguished February was a near historic absence of warmth. The highest temperature of the month, 46, and that was the lowest February maximum in Philadelphia since 1978.
Last month marked only the seventh time in the period of temperature records, which date to 1872, that the temperature failed to reach 50 at least once. The others were 2003; the aforementioned 1978; 1969; 1934; 1905, and 1901.
In terms of snow this season, the region has witnessed storms over-perform and under-perform this season. So far, this one has none-performed.
The computer models did a decent job of capturing the positioning and track of the coastal storm, which is generating impressive winds. The National Weather Service has issued a coastal flood warning for the Shore, with moderate tidal flooding anticipated tonight.
But precipitation amounts have been paltry. As of 11, what has fallen at Philadelphia International Airport has been barely measureable.
As has often been the case this winter, a storm looks to jog a tad more toward the northwest than previously forecast.
The upshot is that up to 2 inches of wet snow is possible across the region from a storm approaching Cape Hatteras. Here is the lastest National Weather Service forecast map.
A mix of snow and rain should get under way this evening and then perhaps change to snow later tonight. But hold the salt.